How does one remove the need to specify the ResponseStatus property in each Response object and utilize fluent validation which adds Validation errors to this property? Suggestions?

You don't need to include a ResposneStatus property as long as your response DTO does not have a "Response" suffix, explained in: https://github.com/ServiceStack/ServiceStack/wiki/Error-Handling#error-response-types

When an exception is thrown and the Response DTO doesn't have a ResponseStatus property it throws a generic ErrorResponse DTO which does.

Bruce Hunter:

Sweet, thanks for the answer. I was looking for this, my brain must not be working today.